Fully Anisotropic Overall Molecular Tumbling with Group Internal Rotation-¹³C Spin-Lattice Relaxation Study of Codeine

¹³C NMR relaxation parameters of codeine were obtained at 90.1 MHz and 62.9 MHz resonance frequencies, Stable molecular motional states were studied The experimental results were analysed by using our model. The molecular rotational rates about axies R₁, R₂ and R₃ and the barries to internal rotation were calculated. The effects of solvents on rotational rates were discussed. The practical utiltics of our theoretical model were illustrated.